Results: (1) Chronic granulomatous disease (CGD) is a primary immunodeficiency caused by mutations in the multicomponent NADPH oxidase (phagocyte oxidase, NOX2) complex. During the past FY, through collaboration with the Neutrophil Monitoring Laboratory (NML) managed by Douglas Kuhns, PhD (Leidos, Inc.), we provided molecular diagnoses using immunodetection of components of the NADPH oxidase for 2 p47phox-deficient, and 27 gp91phox-deficient subjects or carriers. Nucleic acid sequencing determined the specific DNA mutations in 46 patients and family members. During FY19, the NML published its paper on a digital droplet PCR-based approach to the sequencing of NCF1, the gene encoding p47phox, that has previously been a serious diagnostic challenge due to the presence of two closely similar pseudogenes (NCF1B and NCF1C). During FY19, the NML also performed functional studies on five CGD patients undergoing lentivirus-mediated gene therapy to monitor efficacy of the approach to correct functional defects in leukocytes, this manuscript is currently under review. Also during FY19, the NML has provided molecular diagnoses for patients with other immunodeficiencies, for example those found to carry mutations in CXCR4 (1 patient), G6PD (Glucose 6-phosphate dehydrogenase, 2 patients), and ELANE (neutrophil elastase,2 patients). The NML is actively studying neutrophil function in cells from patients with Chediak Higashi syndrome, RAC2 mutations, PI3K deficiency and DOCK11 mutations. (2) Our group continues its clinical studies of the emerging Gram-negative CGD pathogen, Granulibacter bethesdensis. We continue to monitor seropositivity in culture-confirmed patients and patients suspected of having a Granulibacter infection to evaluate our hypothesis that this organism can establish persistent, clinically silent infections. Although rare, reported Granulibacter infections in CGD patients have a case fatality rate of 30% suggesting that more work is required to improve diagnosis and treatment of this pathogen. We are examining the prevalence of bacteria in specimens from suspected cases and from other diseases, such as sarcoidosis, with a suspected but as yet unidentified bacterial cause of granulomatous inflammation. (3) Our protocol, (#10-I-0029 Non-invasive Assessment of Atherosclerosis in Patients with CGD and other Disorders of the Immune System) has already demonstrated the contribution of NOX2-dependent ROS to the development of increased carotid vessel wall thickness, a preclinical sign of atherosclerosis that is readily detectable using carotid magnetic resonance imaging. During FY18, we have advanced our clinical efforts on this project by evaluating 34 subjects in a follow up study of measuring preclinical atherosclerosis in carriers of X-linked CGD. X-CGD carriers are generally healthy although lyonization, or X-chromosome inactivation, results in X-CGD carriers having different numbers of normal and CGD-like cells in their circulation. In some cases, where the X-chromosome containing the wild-type allele is inactivated in 90-95% of progenitor cells, the patients can present with a clinical phenotype indistinguishable from CGD. The study of carriers and healthy-age match controls will test the hypothesis that increasing ratios of cells producing ROS positively correlate with the extent of atherosclerosis. We are completing the statistical analysis of these data. (4) Based on the initial results of our clinical study (10-I-0029, , we have been collaborating with investigators at the National Center for Advancing Translational Sciences (NCATS) to identify chemical inhibitors of NOX2. Using a cell line developed by Tom Leto in the LCIM, we developed a lab scale-screening assay for NOX2 activity that then optimized by NCATS for high throughput, robotic screening for inhibitors of NOX2. To date, we have evaluated over 70,000 compounds in primary and secondary screens and are working on variants of lead candidates for further study. Given the high rate of false-positive compounds in the first generation primary screen, we are actively developing several alternative assays for NOX2 that do not rely on indirect measurements of enzyme activity in intact cells but rather focus either on subunit interactions (binding) that are known to regulate assembly of the active enzyme complex or a highly purified enzyme complex with artificial activators that function as a molecularly defined assay instead of a whole cell. We have also performed studies of mouse strains that are genetically deficient in various NOX enzymes to evaluate their contributions to pathogenesis in a model of traumatic brain injury in collaboration with Dr. Dorian McGavern (NINDS). This model has also been used to evaluate lead NOX2 inhibitors and further ongoing experiments to definitively prove the involvement of NOX2 in this process are underway. 5) During FY19, we completed our examination of the role of plasma gelsolin in controlling cellular activation during inflammation. Plasma gelsolin is produced by the same gene that encodes the cytosolic actin-binding protein, gelsolin, that plays a crucial role in the regulation of cellular morphology and motility. The plasma form differs in that it possesses an additional short polypeptide of unknown function. Studies by other investigators have identified a role for gelsolin in the regulation of inflammation and as a positive contributor to innate defenses. We are preparing a manuscript describing gelsolin levels during inflammation in several patient populations as well as the contribution of exogenous gelsolin on the activation state of leukocytes in vitro assessed via FACS for activation markers, cytotoxicity, apoptosis, and adherence.